The Modbus masters can access the process data

of the I/O stations in two different ways:

• Fixed mode: each I/O module in the station

uses a separate register address range, which

requires separate Modbus read/write opera

tions for the modules in the station.

• The dynamic mode allows to pack the data of all

I/O modules in the station in one data structure

that can be exchanged in one single read/write operation.

ABB provides a configurator in the Automation

Builder tool, which allows the configuration of

Modbus TCP I/O stations with the communica

tion interfaces CI521-MODTCP or CI522-MODTCP

in the same style as the AC500 configuration. For

larger applications a Bulk Data Manager tool can

be used. The configuration can be stored in the

communication interface, which allows using

the configured station with any PLC or PC that

supports Modbus TCP. This e.g. allows the use

directly on other controllers or monitoring

systems as e.g. ABB Ability™ Data Center Auto

mation or external systems.